Weekly Papers on Quantum Foundations (39)

This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

Origin of chaos in 3-d Bohmian trajectories. (arXiv:1609.07069v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-24 3:18am GMT

Authors: Athanasios C. TzemosGeorge ContopoulosChristos Efthymiopoulos

We study the 3-d Bohmian trajectories of a quantum system of three harmonic oscillators. We focus on the mechanism responsible for the generation of chaotic trajectories. We demonstrate the existence of a 3-d analogue of the mechanism found in earlier studies of 2-d systems, based on moving 2-d `nodal point – X-point complexes’. In the 3-d case, we observe a foliation of nodal point – X-point complexes, forming a `3-d structure of nodal and X-points’. Chaos is generated when the Bohmian trajectories are scattered at one or more close encounters with such a structure.

String Dualities and Empirical Equivalence

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-9-23 5:13pm GMT

Dawid, Richard (2016) String Dualities and Empirical Equivalence. [Published Article or Volume]

Rethinking Newton’s Principia

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-9-21 4:03pm GMT

Saunders, Simon (2013) Rethinking Newton’s Principia. [Preprint]

Spin-0 to Spin-1/2 Deterministic Dynamics: From Relativistic Quantum Potential to Quantum Stress Tensor. (arXiv:1609.03866v2 [quant-ph] UPDATED)

quant-ph updates on arXiv.org

on 2016-9-21 1:53am GMT

Authors: David L. Bartley

The Bohm/de Broglie theory of deterministic non-relativistic quantum mechanics is broadened to accommodate the free-particle Dirac equation. As with the spin-0 theory, an effective particle rest-mass scalar field in the presence of the spin-1/2 pilot wave is allowed, together with the assumption that the convective current component describes ensemble dynamics. Non-positive excursions of the ensemble density for extreme cases of positive-energy solutions of the Dirac equation are interpreted in terms of virtual-like pair creation and annihilation beneath the Compton wavelength. A specific second-rank tensor is defined in terms of the Dirac spinors for generalizing from simply a quantum potential to a stress tensor required to account for the force of pilot wave on particle. A simple dependence of the stress tensor on a two-component spin pseudovector field is determined. Consistency is found with an earlier non-relativistic theory of objects with spin.

Can non-local correlations be discriminated in polynomial time?. (arXiv:1609.06269v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-21 1:53am GMT

Authors: Alberto MontinaStefan Wolf

In view of the importance of quantum non-locality in cryptography, quantum computation and communication complexity, it is crucial to decide whether a given correlation exhibits non-locality or not. In the light of a theorem by Pitowski, it is generally believed that this problem is computationally intractable. In this paper, we first prove that the Euclidean distance of given correlations from the local polytope can be computed in polynomial time with arbitrary fixed error, granted the access to a certain oracle. Namely, given a fixed error, we derive two upper bounds on the running time. The first bound is linear in the number of measurements. The second bound scales as the number of measurements to the sixth power. The former is dominant only for a very high number of measurements and is never saturated in the performed numerical tests. We then introduce a simple algorithm for simulating the oracle. In all the considered numerical tests, the simulation of the oracle contributes with a multiplicative factor to the overall running time and, thus, does not affect the sixth-power law of the oracle-assisted algorithm.

Atomic “bomb testing”: the Elitzur-Vaidman experiment violates the Leggett-Garg inequality. (arXiv:1609.06218v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-21 1:53am GMT

Authors: Carsten RobensWolfgang AltClive EmaryDieter MeschedeAndrea Alberti

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object — in a dramatic scenario, a bomb — without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality — a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.

Leggett-Garg test of superconducting qubit addressing the clumsiness loophole. (arXiv:1609.05957v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-21 1:53am GMT

Authors: Emilie HuffmanAri Mizel

The Leggett-Garg inequality holds for any macrorealistic system that is being measured noninvasively. A violation of the inequality can signal that a system does not conform to our primal intuition about the physical world. Alternatively, a violation can simply indicate that “clumsy” experimental technique led to invasive measurements. Here, we consider a recent Leggett-Garg test designed to try to rule out the mundane second possibility. We tailor this Leggett-Garg test to the IBM 5Q Quantum Experience system and find compelling evidence that qubit $Q_2$ of the system cannot be described by noninvasive macrorealism.

Note on the structure of the thermodynamic arrow of time in classical and quantum theories. (arXiv:1609.05910v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-21 1:53am GMT

Authors: Kamil Korzekwa

In this work we analyse the structure of the thermodynamic arrow of time, defined by transformations that leave the thermal equilibrium state unchanged, in classical (incoherent) and quantum (coherent) regimes. We note that in the infinite temperature limit the thermodynamic ordering of states in both regimes exhibits a lattice structure. This means that when energy does not matter and the only thermodynamic resource is given by information, the thermodynamic arrow of time has a very specific structure. Namely, for any two states at present there exists a unique state in the past consistent with them and with all possible joint pasts. Similarly, there also exists a unique state in the future consistent with those states and with all possible joint futures. We also show that the lattice structure in the classical regime is broken at finite temperatures, i.e., when energy is a relevant thermodynamic resource. Surprisingly, however, we prove that in the simplest quantum scenario of a two-dimensional system, the lattice structure is preserved at finite temperatures. This leads to a question about the role coherence plays in providing structure to the thermodynamic arrow of time. In developing our results we find necessary and sufficient geometric conditions for the existence of a single-qubit CPTP map with a given fixed point.

A pragmatist view of the metaphysics of entanglement

Latest Results for Synthese

on 2016-9-21 12:00am GMT

Abstract

Quantum entanglement is widely believed to be a feature of physical reality with undoubted (though debated) metaphysical implications. But Schrödinger introduced entanglement as a theoretical relation between representatives of the quantum states of two systems. Entanglement represents a physical relation only if quantum states are elements of physical reality. So arguments for metaphysical holism or nonseparability from entanglement rest on a questionable view of quantum theory. Assignment of entangled quantum states predicts experimentally confirmed violation of Bell inequalities. Can one use these experimental results to argue directly for metaphysical conclusions? No. Quantum theory itself gives us our best explanation of violations of Bell inequalities, with no superluminal causal influences and no metaphysical holism or nonseparability—but only if quantum states are understood as objective and relational, though prescriptive rather than ontic. Correct quantum state assignments are backed by true physical magnitude claims: but backing is not grounding. Quantum theory supports no general metaphysical holism or nonseparability; though a claim about a compound physical system may be significant and true while similar claims about its components are neither. Entanglement may well have have few, if any, first-order metaphysical implications. But the quantum theory of entanglement has much to teach the metaphysician about the roles of chance, causation, modality and explanation in the epistemic and practical concerns of a physically situated agent.

Indistinguishability

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-9-19 5:05pm GMT

Saunders, Simon (2013) Indistinguishability. [Preprint]

The Higgs mechanism and superconductivity: A case study of formal analogies

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-9-19 5:04pm GMT

Fraser, Doreen and Koberinski, Adam (2016) The Higgs mechanism and superconductivity: A case study of formal analogies. [Published Article or Volume]

On conservation laws in quantum mechanics. (arXiv:1609.05041v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-19 4:05am GMT

Authors: Yakir AharonovSandu PopescuDaniel Rohrlich

We raise fundamental questions about the very meaning of conservation laws in quantum mechanics and we argue that the standard way of defining conservation laws, while perfectly valid as far as it goes, misses essential features of nature and has to be revisited and extended.

Can the Many-Worlds-Interpretation be probed in Psychology?. (arXiv:1609.04878v1 [quant-ph])

quant-ph updates on arXiv.org

on 2016-9-19 4:05am GMT

Authors: Heinrich Päs

A minimal approach to the measurement problem and the quantum-to-classical transition assumes a universally valid quantum formalism, i.e. unitary time evolution governed by a Schr\”odinger-type equation. As had been pointed out long ago, in this view the measurement process can be described by decoherence which results in a “Many-Worlds” or “Many-Minds” scenario according to Everett and Zeh. A silent assumption for decoherence to proceed is however, that there exists incomplete information about the environment our object system gets entangled with in the measurement process. This paper addresses the question where this information is traced out and – by adopting recent approaches to model consciousness in neuroscience – argues that a rigorous interpretation results in a modern perspective on the von-Neumann-Wigner interpretation – namely that the information that is or is not available in the consciousness of the observer is crucial for the definition of the environment. As such the quantum-to-classical transition while being difficult or impossible to probe in physics may become testable in psychology.

Revisiting the Applicability of Metaphysical Identity in Quantum Mechanics

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-9-18 5:29pm GMT

da Costa, Newton C. A. and de Ronde, Christian (2016) Revisiting the Applicability of Metaphysical Identity in Quantum Mechanics. [Preprint]

 

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